Design, fabrication and characterization of a low-temperature co-fired ceramic gaseous bi-propellant microthruster

A gaseous bi-propellant chemical microthruster was developed using low-temperature co-fired ceramic (LTCC) tapes. A sapphire window and silver spark ignition electrodes were successfully co-fired in the LTCC microthruster. Thrust outputs between 0.2 mN and 1.97 mN could be achieved from the 9.9 mm3 thrust chamber by hot-gas operation using ethylene-argon/oxygen mixtures. A non-premixed combustion scheme was utilized by applying an inlet configuration with offset opposing fuel and oxidizer ports. The inlet port design was able to facilitate the generation of swirling flow. Fuel/oxidant mixing could be enhanced in the thrust chamber with the swirling streams according to the cold-flow multi-species 3D computational fluid dynamics (CFD) analysis. Flame chemiluminescence measurements through the transparent observation window were performed to characterize the flame structure in the miniature combustion chamber. The flame zone was found to coincide with the stoichiometric plane predicted by the CFD simulations. Thrust measurements were accomplished by measuring the impingement force of the exhaust jet on a precision balance. The disturbance introduced by the tubing and wiring on the continuous flow microthruster could therefore be eliminated. Thrust was linearly proportional to the total mass flow rate of the inlet. The chemical energy input of the microthruster was approximately 37 W for the maximal measured thrust of 1.97 mN.